CHAP. xiv. IN PHYSICAL GEOGRAPHY. 275 



this region is of such moderate elevation above the sea, that 

 it would be almost equally laid under water, were there a 

 sinking of no more than 600 feet. 



To make this last proposition clear, I have constructed, 

 from numerous documents, many of them unpublished, the 

 map, fig. 40, given at p. 278, which shows how that small 

 amount of subsidence would reduce the whole of the British 

 Isles to an archipelago of very small islands, with the excep 

 tion of parts of Scotland, and the north of England and Wales, 

 where four islands of considerable dimensions would still 

 remain. 



As to the district south of the Thames and the Bristol 

 Channel, it seems to have remained land during the whole of 

 the glacial period at a time when the northern area was 

 under water. 



The map, fig. 40, p. 278, just alluded to, represents 

 simply the effects of a downward movement of a hundred 

 fathoms, or 600 English feet, supposed to have been uniform 

 over the whole of the British Isles. It shows the very dif 

 ferent state of the physical geography of the area in question, 

 when contrasted with the results of an opposite movement, 

 or one of upheaval, to an equal amount, of which Sir Henry 

 de la Beche had already given us a picture (from which I 

 have borrowed the map, fig. 41, p. 279), in his excellent 

 treatise called ' Theoretical Eesearches.' * 



If we are surprised when looking at the first map, fig. 40 

 at the vast expanse of sea which so moderate a subsidence 

 as 600 feet would cause, we shall probably be still more 

 astonished to perceive, in fig. 41, that a rise of the same 

 number of feet would unite all the British Isles, including 

 the Hebrides, Orkneys, and Shetlands, with one another and 

 the continent, and lay dry the sea now separating Great 

 Britain from Sweden and Denmark. 



* Also repeated in De la Beche' s Geological Observer. 

 T 2 



